Render Function APIs

h()

Creates virtual DOM nodes (vnodes).

  • Type

    ts
    // full signature
function h(
  type: string | Component,
  props?: object | null,
  children?: Children | Slot | Slots
): VNode

// omitting props
function h(type: string | Component, children?: Children | Slot): VNode

type Children = string | number | boolean | VNode | null | Children[]

type Slot = () => Children

type Slots = { [name: string]: Slot }

    Types are simplified for readability.

  • Details

    The first argument can either be a string (for native elements) or a Vue component definition. The second argument is the props to be passed, and the third argument is the children.

    When creating a component vnode, the children must be passed as slot functions. A single slot function can be passed if the component expects only the default slot. Otherwise, the slots must be passed as an object of slot functions.

    For convenience, the props argument can be omitted when the children is not a slots object.

  • Example

    Creating native elements:

    js
    import { h } from 'vue'

// all arguments except the type are optional
h('div')
h('div', { id: 'foo' })

// both attributes and properties can be used in props
// Vue automatically picks the right way to assign it
h('div', { class: 'bar', innerHTML: 'hello' })

// class and style have the same object / array
// value support like in templates
h('div', { class: [foo, { bar }], style: { color: 'red' } })

// event listeners should be passed as onXxx
h('div', { onClick: () => {} })

// children can be a string
h('div', { id: 'foo' }, 'hello')

// props can be omitted when there are no props
h('div', 'hello')
h('div', [h('span', 'hello')])

// children array can contain mixed vnodes and strings
h('div', ['hello', h('span', 'hello')])

    Creating components:

    js
    import Foo from './Foo.vue'

// passing props
h(Foo, {
  // equivalent of some-prop="hello"
  someProp: 'hello',
  // equivalent of @update="() => {}"
  onUpdate: () => {}
})

// passing single default slot
h(Foo, () => 'default slot')

// passing named slots
// notice the `null` is required to avoid
// slots object being treated as props
h(MyComponent, null, {
  default: () => 'default slot',
  foo: () => h('div', 'foo'),
  bar: () => [h('span', 'one'), h('span', 'two')]
})

  • See also: Guide - Render Functions - Creating VNodes

mergeProps()

Merge multiple props objects with special handling for certain props.

  • Type

    ts
    function mergeProps(...args: object[]): object

  • Details

    mergeProps() supports merging multiple props objects with special handling for the following props:

    • class
    • style
    • onXxx event listeners - multiple listeners with the same name will be merged into an array.

    If you do not need the merge behavior and want simple overwrites, native object spread can be used instead.

  • Example

    js
    import { mergeProps } from 'vue'

const one = {
  class: 'foo',
  onClick: handlerA
}

const two = {
  class: { bar: true },
  onClick: handlerB
}

const merged = mergeProps(one, two)
/**
 {
   class: 'foo bar',
   onClick: [handlerA, handlerB]
 }
 */

cloneVNode()

Clones a vnode.

  • Type

    ts
    function cloneVNode(vnode: VNode, extraProps?: object): VNode

  • Details

    Returns a cloned vnode, optionally with extra props to merge with the original.

    Vnodes should be considered immutable once created, and you should not mutate the props of an existing vnode. Instead, clone it with different / extra props.

    Vnodes have special internal properties, so cloning them is not as simple as an object spread. cloneVNode() handles most of the internal logic.

  • Example

    js
    import { h, cloneVNode } from 'vue'

const original = h('div')
const cloned = cloneVNode(original, { id: 'foo' })

isVNode()

Checks if a value is a vnode.

  • Type

    ts
    function isVNode(value: unknown): boolean

resolveComponent()

For manually resolving a registered component by name.

  • Type

    ts
    function resolveComponent(name: string): Component | string

  • Details

    Note: you do not need this if you can import the component directly.

    resolveComponent() must be called inside either setup() or the render function in order to resolve from the correct component context.

    If the component is not found, a runtime warning will be emitted, and the name string is returned.

  • Example

    js
    const { h, resolveComponent } = Vue

export default {
  setup() {
    const ButtonCounter = resolveComponent('ButtonCounter')

    return () => {
      return h(ButtonCounter)
    }
  }
}
    js
    const { h, resolveComponent } = Vue

export default {
  render() {
    const ButtonCounter = resolveComponent('ButtonCounter')
    return h(ButtonCounter)
  }
}

  • See also: Guide - Render Functions - Components

resolveDirective()

For manually resolving a registered directive by name.

  • Type

    ts
    function resolveDirective(name: string): Directive | undefined

  • Details

    Note: you do not need this if you can import the component directly.

    resolveDirective() must be called inside either setup() or the render function in order to resolve from the correct component context.

    If the directive is not found, a runtime warning will be emitted, and the function returns undefined.

  • See also: Guide - Render Functions - Custom Directives

withDirectives()

For adding custom directives to vnodes.

  • Type

    ts
    function withDirectives(
  vnode: VNode,
  directives: DirectiveArguments
): VNode

// [Directive, value, argument, modifiers]
type DirectiveArguments = Array<
  | [Directive]
  | [Directive, any]
  | [Directive, any, string]
  | [Directive, any, string, DirectiveModifiers]
>

  • Details

    Wraps an existing vnode with custom directives. The second argument is an array of custom directives. Each custom directive is also represented as an array in the form of [Directive, value, argument, modifiers]. Tailing elements of the array can be omitted if not needed.

  • Example

    js
    import { h, withDirectives } from 'vue'

// a custom directive
const pin = {
  mounted() {
    /* ... */
  },
  updated() {
    /* ... */
  }
}

// <div v-pin:top.animate="200"></div>
const vnode = withDirectives(h('div'), [
  [pin, 200, 'top', { animate: true }]
])

  • See also: Guide - Render Functions - Custom Directives

withModifiers()

For adding built-in v-on modifiers to an event handler function.

  • Type

    ts
    function withModifiers(fn: Function, modifiers: string[]): Function

  • Example

    js
    import { h, withModifiers } from 'vue'

const vnode = h('button', {
  // equivalent of v-on.stop.prevent
  onClick: withModifiers(() => {
    // ...
  }, ['stop', 'prevent'])
})

  • See also: Guide - Render Functions - Event Modifiers